ELECTROLYTIC DISSOCIATION 37 



limit. The evidence to be obtained from the study of the 

 kinetics of chemical reaction all appears to favor the theory. 

 9. New ideas are introduced with regard to chemical equi- 

 librium. The laws of dissociation, where gases are concerned, 

 lead to the well-established postulate that dissociation shall 

 be greatest where the atmosphere contains no excess of either 

 of the constituents into which the molecule will break up; dis- 

 sociation is unaffected by the presence of any other indiffer- 

 ent substances. By analogy, if a solution already contains a 

 number of free ions of a particular sort, any substance con- 

 sisting in part of this same sort of ions will not dissociate as 

 fully as in pure water. Consequently an acid will be weak- 

 ened by the presence of one of its neutral salts, but the effect 

 will be much more perceptible for a weak acid than for a 

 strong one. This has been verified by Arrhenius. Comparing 

 on the other hand, acids which have the positive ion H in 

 common, a mixture of the two must affect their respective 

 degrees of dissociation, unless before mixing the H had the 

 same osmotic partial pressure in both solutions. This means 

 that there shall be the same degree of dissociation in the 

 two solutions, that they shall be "isohydric." Under such 

 conditions, if ra parts of one solution having the conductivity 

 a be mixed with n parts of the other having the conductivity 

 6, the resulting solution will conduct as if each electrolyte 

 were conducting independently and unchanged. Its conductiv- 

 ity is - , no matter what the relative values of m and 

 m+n 



n are. Furthermore, if two solutions are "isohydric" with a 

 third, they must be isohydrous with each other. These two 

 consequences have been substantiated by the examination 

 of the conductivity of mixtures of "isohydric" solutions of 

 acids with one another and with those of their respective 

 neutral salts, of neutral salts with one another and with the 



